Certain pyridinium derivatives of cycloheptyl-imidazoles

ABSTRACT

The present invention encompasses certain 2-aryl or 2-pyridinium cycloheptyl-imidazoles. These compounds may be prepared by reacting 2-halogeno-tropone or 2-methoxy-tropone with the appropriately substituted amidine. They are useful as desensitizers for light sensitive silver halide photographic materials.

United States Patent Soma et al.

1451 Oct. 24, 1972 CERTAIN PYRIDINIUM DERIVATIVES OFCYCLOHEP'TYL-IMIDAZOLES Filed: March 13,1967

Appl. No; 622,475

Foreign Application Priority Data March 19, 1966 Japan ..41/17040 US.Cl. ..260/295.5, 260/296, 260/309,

96/62, 96/10], 260/2955 AM Int. Cl. ..C07d 31/44, G03c 5/32 Field ofSearch ..260/296 B, 296 C, 295.5 B, 260/2955 C, 295 B, 295 C, 295 AMReferences Cited OTHER PUBLICATIONS Sunagawa et al. Chem. Abstracts (I),Vol. 64, Par. 3551-g to 3552-a, (1966, January) Nakao et al. Chem.Abstracts (ll) Vol. 63, Par. 4227, Aug. 1965 Soma et al. Chem. Abstracts(111) Vol. 63, Par.

- 13142-13143. Nov. 1965 Primary Examiner-Henry R. Jiles AssistantExaminer-Alan L. Rotman Attorney-Waters, Roditi, Schwartz & Nissen [57]ABSTRACT The present invention encompasses certain 2-aryl or2-pyridinium cycloheptyl-imidazoles. These compounds may be prepared byreacting 2-halogenotropone or 2-methoxy-tropone' with the appropriatelysubstituted amidine. They are useful as desensitizers for lightsensitive silver halide photographic materials.

1 Claim, No Drawings CERTAIN PYRIDINIUM DERIVATIVES OFCYCIJOHEYIYL-IMIDAZOLES This invention relates to a desensitizer for alight-sensitive silver halide photographic material, said desensitizerhaving the chemical structure represented by the below-mentioned generalfonnula (I). It is the principal object of the present invention toprovide a desensitizer, which does not cause any staining or colorationof photographic pictures and which has no adverse influence on thecontrast of photographed images.

Heretofore, a number of compounds have been known useful asdesensitizers for light-sensitive silver halide photographic materials,which compounds include, for example phenosafranine, malachite green,pinacryptol yellow, pinacryptol green, etc. These known compounds, thatis the desensitizers, suffer from several drawbacks and are notsatisfactory in their actual use. For instance, some of thesedesensitizers will stain or color the photographic picture or willimpair the photographic properties of the resulting image, because theirbeing inherently colored substances. More concretely, phenosafraninewhich is a substance having red color usually causes reddish colorationof the photographic materials, sometimes with decrease in contrast ofthe photographed images. Marachite green and pinacryptol green, both ofwhich are green compounds, will decrease whiteness of the background ofphotographic pictures. Furthermore, pinacryptol green sometimes has anadverse effect against stability of a fogged emulsion. Pinacryptolyellow, which is a generally preferred known desensitizer because of itsraising no problem in contrast of photographic images, will causeyellowish coloration to decrease whiteness of the surface ofphotographic materials. Moreover, it has a serious drawback that isunstability in a developing solution. Thus, all the known desensitizersare not satisfactory because of their undesired influence on thephotographic properties of the resulting images.

In accordance with the present invention, there is provided a newdesensitizer having the following chemical structure:

g i R -R2 2 wherein R, is hydrogen, lower alkyhhalogen, cyano ordialkylamino and R is aryl or pyridinium group which may be substituted.v

The compounds defined above are available at rela- 5 'tively cheapcosts. Almost all of these are colorless substances, and other few aresuch substances as having very slight color, insufficient to causecoloration. The compounds can meet the following photographicrequirements:

1. They should have a capability to decrease photocrystals;

4. They should not contaminate binders (e.g.,

gelatine).or supports; and 5. They shouldbesolubleinwa'ter. It is, ofcourse, possible to use the compounds in a developing solution.

A compound of the above general formula (I) wherein R is substituted. orunsubstituted aryl group can be prepared according to the methoddescribed in Japanese Patent Publication No. 20706/ 1965, that is, bythe reaction of 2-halogenoor 2-methoxy-tropone of the general formula(wherein X is halogen or methoxy and R; is defined as 1 above) with anamidine of the general formula 40 (wherein R is defined as above). Acompound of the .be optionally substituted with alkyl, halogen, nitro,al-

koxy, carbamoyl, alkoxycarbonyl, etc. Typical compounds comprehended bythe present invention are as i llqfiufl M.p. 162 C2-phenylcycloheptimidazole.

M.p.153 c.

2-pheny14-4bromocycloheptlmidazole.

M.p. 267 C. (decomp.)

2-(m-nitrophenyl)cycloheptimidazole.

' M.p. 204 C.

2-(p-bromophenyl)eycloheptimidazole.

These compounds can. be used as desensitizers for photographic purposesin the same manner as the conventionally known desensitizers forlight-sensitive silver halide photographic materials. For example, anexposed high-speed photographic film can be pretreated with an aqueoussolution of a desensitizer of the present invention so that said filmmay be developed under relatively bright condition which enables us toconduct developing with visual inspection of the progress ofdevelopment. Alternatively, the desensitizer can be added to adeveloping solution to be used for photographic development, whereby anexposed photographic film can be treated with said solution underrelatively bright condition because of its decreased sensitivity.Incorporation of the desensitizer into a light-sensitive silver halidephotographic emulsion having fogged silver halide crystals can provideus with a direct positive, light-sensitive material which directlyyields a positive image through Herschel effect or solarization.

If a desensitizer of the present invention is used as a pretreating bathfor imagewise exposed, light-sensitive silver halide photographicmaterials, it is conveniently prepared in the form of an aqueoussolution at a concentration of 0.01-0.03 percent. After dipping in thissolution for several minutes, the photographic material can be treatedwith a conventional developing solution under relatively brightsafelight. If the desensitizer is used in a developing solution, itshould be in amount of 0.003 to 0.02 percent. By use of a desensitizerof the invention, the developing procedures can be taken under suchbright safelight which allows us to make visual inspection of the resultof the developed images. Of course, there is no problem of coloration ofdeveloped images or of, any damage on the contrast of the images.

For the preparation of a direct positive lightsensitive photographicmaterial, a desensitizer of the invention is used in the amount of0005-1 g. per 100 g. of silver nitrate the amount of which is calculatedfrom the silver halide content of the light-sensitive emulsion used. Theappropriate amount of the desensitizer is dissolved in water or loweralcohol or the mixture of both and the resulting solution is added tothe light-sensitive emulsion containing fogged silver halide crystals.Usually it is preferred to combine the desensitizer solution with thefogged emulsion just before the coating of the resulting mixture on asupport, but this is not critical. The thus prepared direct-positivelight-sensitive material can show well improved Herschel effect, bywhich an image free from any coloration and with high contrast isobtained.

The following examples described certain ways in which the principle ofthe invention has been applied, but are not to be construed as limitingits scope.

EXAMPLE 1 2-(m-Nitrophenyl)-cycloheptimidazole was prepared as 0.02percent aqueous solution, into which a commercially available,high-speed panchromatic photographic film was dipped for 2 minutes,thereby to have its original sensitivity decreased to 1/100. Thus,

Alternatively, 0.1 g. of 2-(m-nitrophenyl)-cycloheptimidazole was addedto a developing solution of the following formulation:

Monomethyl-p-aminophenol sulfate 2.0 g. Sodium sulfite (anhydrous) 80.0g. l-lydroquinone 4.0 g. Borax 4.0 g.

Potassium bromide 0.5 g.

; Distilled water to make up 1000 ml.

By using the resulting mixture, a commercially available high-speedpanchromatic photographic film was treated. 'The procedures could bemade under relatively bright safelight condition, without causing anycoloration or contamination.

. EXAMPLE 2 5 of an aqueous solution of 10 percent citric acid. The

emulsion was divided to ten portions, each of which was added with thecompound indicated in Table l. The respective portions were coated onphotographic papers and then dried. The thus prepared direct positive,light-sensitive photographic sheets were subjected to stepwise exposureto light through a yellow filter which can pass a light of a wave lengthlonger than 450mg. and then treated with a D-72 type developer.

5 The sensitometric results obtained are set forth below:

the treated film could be subjected to development under relativelybright safelight. After the development, the films did not show anycoloration or contamination.

Pinacryptol yellow and phenosafranine were used as the controldesensitizers.

This was expressed as a specific value in compared with the reversalphotographic speed of the pinacryptol yellow-loaded photographic sheet,which is rated as l00.

As apparent from the above table, the sheets in which the desensitizersof this invention were used were excellent in photographic speedandcontrast, whereas the control sheets loaded with pinacryptol yellowand phenosafranine suffered respectively from yellowish or reddishcoloration.

EXAMPLE 3 One kilogram of a pure silver chloroiodide emulsion containingthe equivalent to 40 g. of silver nitrate was bufiered to pH 7.5 by theaddition of of 5 per cent aqueous sodium carbonate solution. Then, theemulsion was added with 10 ml. of 3 percent formalin and heated at 55 C.for 40 minutes. The thus fogged emulsion was buffered to pH 6.0 by theaddition of an aqueous solution of 10 percent citric acid. The emulsionwas divided to 10 portions, each of which was added with the compoundindicated in Table 2. The respective portions were coated onphotographic papers and then dried. The thus prepared ten directpositive, light-sensitive photographic sheets were subjected to stepwiseexposure to white light and then treated with a developing solution. Thesensitometric results obtained are below:

w what we claim are: H W W l. A compound of the formula;

Compds. (10) 20 mg 1120 3.74 0.0l Compds. (l l) 20 mg I050 3.62 0.02Compds. (16) 20 mg 1090 3.69 0.01

which the desensitizers of the invention were used were more excellentin reversal minimum density and contrast, whereas the control sheetssuffered from coloration of their surfaces.

wherein R is hydrogen or 6-positioned dimethylamino

